Majeed K, Bellinge JW, Butcher SC, et al. - Micro-calcification activity, the earliest stage of atherosclerotic arterial calcification, can be non-invasively detected using 18F-Sodium Fluoride Positron Emission Tomography (18F-NaF PET). The association between coronary 18F-NaF uptake and high-risk plaque features on intra-coronary optical coherence tomography (OCT) and CT-angiography (CTCA) was studied and the potential application to patient-level risk stratification was determined. Multi-vessel OCT, 18F-NaF PET and CTCA were performed on 62 prospectively recruited patients with acute coronary syndrome (ACS). In these patients, the coronary segments with increased 18F-NaF uptake had higher lipid arc (LA), higher prevalence of macrophages and lower plaque free wall (PFW) on OCT, and a higher total plaque burden and higher dense calcified plaque burden on CTCA, in comparison with 18F-NaF negative segments. Decreasing plaque free wall, increasing calcification and increasing macrophages on OCT were identified in patients grouped by increasing number of coronary lesions positive for microcalcification activity (0,1, ≥ 2). Overall, observations suggest correlation of 18F-NaF uptake with high-risk plaque features on OCT and CTCA in a per-segment and per-patient analysis in patients hospitalized for ACS.